High-Rise - J.G. Ballard

“If you want to go higher, I’ll show you. There are a lot of air-shafts, you know. The trouble is, dogs have got into them—they’re getting hungry…”

This is... the slow rising level of insanity, and then comments like this, that make you realize how really nutty things are.

"While his neighbours on the lower floors remained a confused rabble united only by their sense of impotence, here everyone had joined a local group of thirty adjacent apartments, informal clans spanning two or three floors based on the architecture of corridors, lobbies and elevators. There were now some twenty of these groups, each of which had formed local alliances with those on either side. There was a marked increase in vigilante activity of all kinds. Barriers were being set up, fire-doors locked, garbage thrown down the stairwells or dumped on rival landings."